CHEMICAL PROPERTIES OF FATTY ACIDS AND RELATED COMPOUNDS 141 



The iiitrile may likewise be prepared directly from the fatty acid without 

 the actual isolation of the amides. This reaction can be accomplished 

 when fatty acids and ammonia interact at high temperatures in either the 

 liquid or the vapor phase. When the fatty acids are heated in a continu- 

 ous stream of ammonia at a temperature at which the amide first formed is • 

 decomposed, a quantitative transformation to the nitrile eventually obtains. 

 The nitriles are likewise synthesized when the fatty acids or their esters are 

 passed, in their vapor phase, with ammonia, over such contact catalysts as 

 pumice, alumina, thoria, or silica gel at a temperature of 400°C. or higher. 



The nitrile is formed when aliphatic aldehydes and ammonia are passec^ 

 over thoria or aluminum.*^" The primary and secondary amines, in the^ 

 presence of a nickel catalyst, lose hydrogen, with the production of ni- 

 triles. ^^^ Nitriles originate when equimolecular mixtures of fatty acid es- 

 ters and primary amines are heated to 500 °C. in the presence of dehydra- 

 ting catalysts. ^^- 



Alkyl halides have long been known to react with inorganic cyanides to 

 give the nitriles. The compound so synthesized contains one more carbon 

 atom than the alkyl halide. This reaction has been widely employed for 

 the synthesis of compounds which do not occur naturally. For example, 

 it constitutes an excellent procedure for the preparation of the fatty acids 

 with an odd number of carbon atoms. 



Hofmann^-^ discovered that, when the aliphatic amides or amines are 

 treated with an excess of bromine, nitriles with one less carbon are formed. 

 Aldoximes, such as RCH:NOH, lose a molecule of water in the presence of 

 a dehydrating agent, to give rise to nitriles. Letts^^'* has demonstrated the 

 production of nitriles along with amides when fatty acids are treated with 

 alkali salts of thiocyanic acid. Phenylhydrazones, also, have proved to be 

 useful starting materials since, in the presence of cuprous chloride, they 

 yield a mixture of nitriles and amines. ^^^ 



b'. Properties of Nitriles: The nitriles, including lauronitrile, are 

 liquids at ordinary temperatures. They have a characteristic odor, which 

 is most pronounced in the case of valeronitrile; the solid nitriles (myris- 

 tonitrile and above) are odorless. The melting points (or freezing points) 

 of the several nitriles in °C. are as follows: butyronitrile, —112.6; valero- 

 nitrile, — 96.0; capronitrile, —79.4; caprylonitrile, —45.6; pelargono- 

 nitrile, —34.2; caprinitrile, —14.5; lauronitrile, 4.0; myristonitrile, 19.2; 

 palmitonitrile, 31.4; stearonitrile, 40.9; arachidonitrile, 48.5-49.5; doco- 



520 A. Mailhe, Compt. rend., 166, 36-38, 121-123 (1918). A. Mailhe and F. de Godon, 

 Coyyipt. rend., 166, 215-217 (1918). 



521 A. Mailhe and F. de Godon, Compt. rend., 165, 557-559 (1917). 

 6" A. Mailhe, Compt. rend., 170, 813-815 (1920). 



5" A. W. Hofmann, Ber., 17, 140&-1412 (1884). 



"4 E. A. Letts, Ber., 5, 669-674 (1872). 



"* A. E. Arbusow, Ber., 43, 2296-2300 (1910). 



